INS

Question 1

INTEGRATION VELOCITY

Answer 1

~gives change of position
~present positon relative to a known starting positon
~integration of vertical velocity gives vetical distance travelled

Question 2

Measuring velocuity

Answer 2

~starting velcoity and size of the accelrretion need to be known

Question 3

Types of inertial system

Answer 3

~inertial navigation system (INS) :gyro stabilise platform
~inertial reference system (IRS):
Platform integrated into the flight management system
Know as strap down system as they are fixed units

Answer 4

Stablised platform usually found in old INS
The strap down system usually found in modern IRS

Answer 5

Long range a/c need at least 2 IRS

Answer 6

It can also provide attitude and heading since is a gyroscope INS

Question 7

Electromechanical sensors ,accelerometers

Answer 7

~an electromechanical accelerometer uses a pendulum arrangemnt to detect accelration in one dimesion
~at the bottom of the pendulm has a pick off

Answer 8

1st integration to find&raquo_space;velocity (time x accel)
2nd intergration to find distance(distance) (which gives the lattitude. In the N/s acceloretemet)

And then the intergration is done for the E/W accelrotmeter and is fed the lattitude to find the chlong (depart x secnat lat0

Answer 9

The gyro platfrom is orientated to the true north and the a/c has the database of tthe avriation to get the magnetic north

Answer 10

Gyro stabilisation using 3 RATE integration gyros
One gyro detecs rotation about the east /west axis
One north/south axis
One vertical axis ,in the horizontal azimuth plane

Question 11

Rate intergratiting gyros

Answer 11

Output angle is proportioanl to the amount of change of the iput angle

~output rotation is greater than input rotation
Much more sentive than displacemnt gyro

Answer 12

A torque motor opposes themotion of the output axis

Question 13

Intial alignment

Answer 13

~the a/c must be stationary:
-instial power up (caging)
-levelling
-gyro compassing

Question 14

Gyro compassing

Answer 14

~aligning the platform to true north
~topple is sensed by platform
~if properly aligned to ttrue north the platform would be slowly rotating around its north/south axis
~apparent topple caused by rotation of the earth
~should be no rotaion around the east/west axis
~any roation must be due to misalignmnet

Question 15

Effect of latitude during alignment

Answer 15

~less tople at high laititudes
~aligmnetn is less accuarte
~takes longer
~alignmnet not possible at very high latitudes
Once aligned ,an ins can be operatated at thigh latitudes
Aligmmnet take like 10/20 min at mid lat

In motion alignmnet cannot be carried out with an INS

Answer 16

XTk/TKE
Xtk: how far off are you form the desired track
Tke : how much turn you need to get the desired track

Answer 17

Dsrtk/sts
Left/right

Answer 18

At 2 minute for the next waypoint the the amber light will start to flash ,if in auto

In manual mode,the alert light will remian lit and the a/c will contune on current track and will not turn towards the next waypoint

Question 19

Bounded error

Answer 19

When the longitude is inserted wrongly result in a constant error

Question 20

Unbounded error

Answer 20

Incorrect latitude input error ,making an increase in distance error

Question 21

Input comparison

Answer 21

If calculated and inputted lattitudes dont match ,either
~the alignmnet is bad
~the crew enetered an incorrect latitude

Question 22

Stablised platform variants

Answer 22

~2 accelerometer platform ,common if vertical velocity not required
~displacemnt gyro,obsolute
~wander angle platform ,not aligned with refence to true north
~system detecs topple on both axes to determine orientation
~changes in orientation are tracked

Question 23

Latitude

Answer 23

1 degree of latitude is equal to 60nm

Question 24

Longitude

Answer 24

Chlong (min) = departure /coslat

Question 25

Ground speed

Answer 25

Adding the velocity components togheter
The inertial system calculates groundspeed not tas

Question 26

Inertial system corrections

Answer 26

~topple and drift due to earth rotation
~topple and drift due to transport
~a/c manouvres (changes of attitude or heading)

~additional factors:
~coriolis effect
~centripetal acc
~Schuler oscillation (84,1 min)

Question 27

Erros

Answer 27

~source of error:
-the accuracy pf sensing rotaion raets and acc
-incorect inital longitude /misalignment of the platform
-computational error by ins

~a value for the position error oif am INS is 1/2 nm per hour or more ,or average of 1,5 nm per hour

Question 28

Interial system and reversion

Answer 28

~uses oner AC and one DC supply for aligment
~uses AC for normal operation with DC as a backup
~if AC fails ,the system fails
Unless it has a batetery to keep it alive unitl power is restores